Before going out on the water, warm up on a rowing machine while breathing through your PowerLung. Set it at the highest setting you comfortably can, and as you tire, slowly reduce the resistance of the PowerLung.
This is a great way to combine exercising the lungs you use to breathe and your external muscles at the same time.
Sometimes going out on the water is not an option because of weather or any number of reasons. Others simply are not rowers, but incorporate a rowing machine into their exercise routine. Either way, try using your PowerLung for half of your workout on a rowing machine using the same resistance technique suggested above.